Production of metals and alloys



" Patented June 25, 1940 UNITED STATES PATENT OFFICE PRODUCTION OFMETALS AND ALLOYS No DrawingfApplication August 12, 1935, Se-

rial No. 35,886. Renewed March 27, 1939 14 Claims.

This invention relates to the production of metals and alloys and hasfor an object the provision of a novel and improved method of obtainingor producing metals and alloys from metal compounds or in some casesdirect from their minerals, ores or concentrates, particularlyrefractory metals of the fourth and fifth groups of the periodic system,such as tantalum, columbium, titanium, zirconium, hafnium and vanadium.

Another object of the invention is the provision of a novel method ofproducing a metal by the interaction of its carbide with its oxidewithout melting the metal.

A further object of the invention is the provision and production of ametal alloy wherein the metals are in the same relative proportions asthey occurred in the starting material.

Another object of the invention is to simplify and to expedite theproduction of metals and alloys from their compounds or other sourceswhereby economically to obtain such metals and alloys in commercialform.

Other objects and advantages of the invention will appear more fullyfrom the following de* scription.

The simplified method of the present invention, briefly described,involves the interaction of metal oxide or oxidized metal and metalcarbide or carburized metal at a sub-melting temperature respecting themelting temperature of the metal being produced, whereby to reduce ordeoxidize the metal oxide or oxidized metal and to decarburize the metalcarbide or carburized metal leaving substantially commercial metal.

The carbide and oxide may be made by any suitable methods, or, as willpresently appear, we may use the metal ore or any suitablemetalcontaining mineral or concentrate as the starting material, andprepare or derive either the carbide or the oxide or both the carbideand the oxide therefrom. In proceeding with the description of theinvention, we will describe it in connection with the production oftantalum, 5 columbium and the alloys thereof, it being distinctlyunderstood that except as is particularly pointed out the method issimilarly applicable to the other metals of the fourth and fifth groups,except where it is apparent from the text that 5 the method is solelyapplicable to the particular example chosen.

As already suggested, in preparing the carbide we may use as a startingmaterial a pure, finely divided oxide of tantalum and/or columbium u,made by any suitable method, tantalum and/or columbium ore, or anysuitable tantalumand/or columbium-containing mineral or concentrate.That starting material is carburized by mixing it with suflicientcarbon, preferably in the form of lamp black or powdered coal,completely to reduce or to deoxidize the starting material and toconvert it into a carbide of the same metal or metals when the mixtureis heated to the reducing temperature. When a starting material otherthan the pure oxide is employed, the carbide so produced is termed anunrefined or ore carbide.

The mixture of the starting material and carbon just described is placedin a suitable container or crucible (e. g. a graphite container orcrucible) provided with a vent, and the loaded container is heated tothe reducing temperature for the starting material in a molybdenumwoundtube furnace, in a high frequency furnace, or by other suitable heatingmeans whereby to cause the carbon to react with the starting material.The jreducing temperature for the starting materials just describedabove has been found to range from about 1400 to 2000 C.

During the foregoing reaction carbon monoxide gas is evolved and isburned at the vent of the container and the more volatile constituentsin case a starting material other than the pure oxide is employed arepartially or highly volatilized out of the mixture. The residue wherethe pure oxide was the starting material is a carbide of tantalum and/orcolumbium. Where the ore or a starting material other than the pureoxide is employed, the residue is the unrefined or ore carbide which isa carburized mass with a composition depending upon the originalcomposition of the ore or other starting material minus the oxygen andthe constituents volatilized during the foregoing heat treatment.

That unrefined carbide is refined by pulverizing the ore carbide andsubjecting the pulverulent material to appropriate treatments forremoving undesirable constituents. The precise refining treatment ortreatments form no part of the present invention, and of course willdepend upon the composition of the unrefined carbide and upon theconstituents to be removed therefrom. Any suitable treatments includingsubjecting the pulverulent unrefined carbide to acid baths, leachingtreatments, Wilfley Table treatments, etc., may be employed foreffecting the desired refinement.

It may be well, however, to illustrate the refining operation byreciting here a refinement of an unrefined carbide to producesubstantially pure carbide of tantalum and/or columbium. A typicalunrefined carbide at this stage of our novel method will contain somesilicavvhicn was not volatilize'd during the above described heattreatment, and in addition some iron and manganese which are convertedinto metal or compounds that are readily attacked by mineral acids.Particles or crystals of tantalum carbide, columbium carbide, ortantalum-columbium carbide do not hold iron, manganese, etc., insolution, and those carbides are therefore produced in a pure conditionin the presence of iron, manganese or other impurities which may becontained in the starting material. In other words, the impurities inthe unrefined carbides are merely physically mixed therewith and are notchemically combined. Since mineral acids do not react with or attack thecarbides of tantalum and/or columbium, the pulverized unrefined carbideis treated with hydrochloric acid, aqua regia, and finally withhydrofluoric acid, to remove iron, manganese, silica, and other suchconstituents from the unrefined carbide, thus leaving a refined carbideof tantalum and/or columbium, the relative proportions of the tantalumand columbium being the same as they were in the ore or other startingmaterial.

The oxide for reacting with the carbide is preferably an oxide of themetal or metals in the carbide, although the oxide may be of a differentmetal from that employed in the carbide where it is desired to make analloy of the metal in the carbide with the metal in the oxide. Forexample, tantalum oxide may be interacted with tantalum carbide;columbium oxide may be employed for interaction with columbium carbide;and tantalum-columbium oxide may be employed for interaction withtantalum-columbium carbide, although the oxide of either tantalum orcolumbium may be interacted with the carbide of the other of thosemetals. The oxide may be some of the pure, finely divided oxidedescribed as a starting material from which the carbide could be made,or the oxide may be prepared by any suitable method.

That oxide may be prepared from some of the refined carbide by directlyigniting the carbide and burning out: all of the carbon whereby toconvert the refined carbide into an oxide of the corresponding metal ormetals.

In order to obtain tantalum, columbium, or a tantalum-columbium alloyaccording to our novel method, the carbide of tantalum and/or columbiumand the oxide of tantalum and/or -co1umbium produced as alreadydescribed, or by any suitable methods, are interacted by subjecting abalanced and an intimate mixture thereof to a temperature sufiicient todeoxidize or to reduce the oxide and to decarburize the carbide.Accordingly, the tantalum and/ or columbium carbide and the'tantalumand/or columbium oxide are intimately mixed, for example by grindingthem together in a ball mill in such proportions that the amount ofcarbon in the mixture is substantially equivalent to the amount ofoxygen in the mixture. That is to say; a balanced carbonoxygen mixtureis made by providing about one atom of carbon for every atom of oxygenin the mixture.

That intimately mixed powder is pressed into bars at a pressure of about5 to about 40 tons per square inch on the face of thebar. A hydraulic orother suitablr press may be employed for the pressing operat on.

The bars formed as just described are subjected to a heat treatment. Thepurpose of the heat treatment is to cause the interaction between thecarbide and the oxide in each bar, whereby the carbon and oxygen thereofwill combine to form carbon monoxide, leaving the decarburized and thedeoxidized metal particles in such intimate association that they willreadily combine. We may describe, by way of example, a suitable heattreatment to accomplish that purpose. Each bar is suspended or otherwisesupported in a tube or other suitable container made from a materialhaving a melting temperature which is high with respect to the meltingtemperature of the metal or -metals in the bar. For example, such tubesare made of graphite, tantalum, tungsten, etc., and are preferablyelectrically heated in a suitable electric furnace. For that purpose theends of the tube may be held by heavy water-cooled copper terminalswhich pass through insulated sections of the heat-treating furnace. Forthe production of tantalum or columbium we prefer to use heavy sheettantalum for the tube.

After inserting a container or tube with a bar therein in the furnace,the furnace is evacuated or hydrogen, argon, helium or other suitablegas is streamed therethrough and the heating is commenced. Theatmospheric conditions in the furnace are maintained while the heatingof the bar is continued. When the temperature of reaction between thecarbide and the oxide in the bar is reached there is an evolution ofcarbon monoxide which may be removed by the vacuum pump or pumps or, asthe case may be, with the streaming gas. When the evolution of thecarbon monoxide begins to subside, the temperature of the bar is raisedbut not sufficiently to risk melting the metal. That temperature ismaintained until the vacuum gauge or an analysis ofthe gas stream at theexhaust ,side' of the furnace shows that the carbon monoxide given offby the bar has been substantially entirely removed from the furnace. Forthe production of tantalum and/or columbium we prefer to use thevacuur'n'furnace.

' We find that 1600 C. is a suitable initial temperature of reaction.

After cooling, the bar is removed from the furnace. If the balancebetween the carbide and the oxide has been properly adjusted theresulting metal of tantalum, columbium, or tantalumcolumbium alloy willbe substantially free of both carbon and oxygen. Such metals and alloyshave been prepared by the foregoing method, which show upon chemicalanalysis as little as 0.02% carbon and no oxygen.

Tantalum ore as well as columbium ore is frequently tantalate andcolumbate of iron and manganese with or without small amounts of one ormore of such metals as titanium, zirconium, hafnium, vanadium-and otherrefractory metals, and is conventionally described by the formula (Fe,Mn) (Cb, Tahoe, although such ores range in fine gradations from thesubstantially pure columbate to the substantially pure tantalate. By ournovel method we therefore produce commercial tantalum or columbium, or acommercial alloy of tantalum and columbium, the amount of either of thementioned metals with respect to the other metal varying from negligiblequantities up to substantially and any of those commercial metals oralloys may include small amounts of one or more of the other refractorymetals which were present in the ore or other starting material.

Thus by starting with the ore the resulting product will containtantalum and/or columbium with or without one or more other refractorymetals which were present in the ore in their natural proportions, thatis to say, in the same relative proportions as they occurred in the oreor other starting material, and due possibly to the very intimateassociation of the tantalum and columbium throughout the method as wellas to the tantalum and columbium respectively being in their naturalforms or states, and therefore probably being isomorphous or at leastatomically (in contradistinction with aggregatively) intermixed, theresulting material is exceedingly homogeneous.

It is desirable that the metals and alloys produced as described aboveinclude as small an amount of carbon as possible. We have discoveredthat the amount of carbon in the final product may be controlled byvarying the grain size or mesh of the carbide which is mixed with theoxide just prior to the pressing operation, and/or varying the pressurefor converting the mixed oxide and carbide into bars, and/or by varyingthe amount of the oxide relative to the amount of the carbide in makingthe mixture for pressing.

If desired the bar as formed above may be conditioned either byalternate mechanical workings (e. g. hammering) and one or morerepetitions of the heat treatment last described above, or byhydrogenating it, pulverizing the hydrogenated bar, and dehydrogenatingthe pulverulent mass as described in our United States Patent No.2,107,279. In some cases we condition the deoxidized, decarburizedproduct of the heat treatment by a combination of the conditioningoperations just described. After such conditioning tantalum bars andcolumbium bars made as described above have all of the properties ofcommercial tantalum'and columbium respectively. Bars of combinedtantalum and columbium have a high resistance to corrosion.

It will thus be seen that by the novel method of the inventioncommercial tantalum, commercial columbium, and commercialtantalum-columbium alloy may be economically derived from the respectivecompornds, minerals, ores, or concentrates without melting the productbeing produced. The commercial tantalum-columbium alloy containstantalum and columbium in the same relative proportions as they occurredin the starting material. Being in their natural state and thereforeprobably isomorphous or at least atomically (in contradistinction toaggregatively) intermixed, the tantalum and columbium evidently flowtogether or combine to produce a solid homogeneous product when heattreated as described above.

Wl'iile we have described certain specific furnace constructions andcrucibles in connection with the furnace for interacting the carbide andthe oxide, and for heat treating the resulting metal, it will beunderstood that the method of the invention is by no means limited bythe recitation of such apparatus, the important consideration being tocause tantalum carbide or columbium carbide, to interact either with theoxide of tantalum or the oxide of columbium, or to causetantalum-columbium carbide to interact with the oxide of tantalum andcolumbium, whereby to leave tantalum,,, columbium, or atantalum-columbium alloy. As pointed out above, the method is applicableto the production of titanium, zirconium, hafnium and vanadium as wellas tantalum and columbium, or to any metal or alloy the carbide andoxide of which have an interacting temperature below the meltingtemperature of the metal and the oxide, and where the oxide has avolatilization temperature sufficiently high to prevent the removal ofan appreciable quantity of the oxide as such from the mixture at theinteracting temperature.

It will thus be seen that by the novel method of the invention,commercial metal, either as a single metal or as a combination ofmetals, may be economically derived from metal compounds. Where aplurality of metals is included in the commercial metal or finalproduct, the metals thereof are present in the same relative proportionsas they occurred in the starting materials or compounds.

While we have described a preferred embodimerit of the invention, manymodifications may be made without departing from the spirit of theinvention. The invention is not, therefore, limited to the precisedetails set forth above, but includes all changes within the spirit andscope of the appended claims.

Having thus described our invention, what we claim as new and desire tosecure by United States Letters Patent is:

1. The improvement in the art of producing refractory metal of thefourth and/or fifth groups which includes pressing, to the form of acoherent bar, a carbon-oxygen balanced powdered mixture of carbide andoxide of the metal being produced, furnace heating the bar to causeinteraction of the carbide and oxide at a temperature below thetemperature at which the oxide volatilizes as such, and then, after thereaction is largely completed, raising the temperature of. the bar to apoint below the melting point of the metal being produced to completethe reaction.

2. The improvement in the art of producing refractory alloys of thefourth and/or fifth groups, which consists in forming a carbon-oxygenbalanced mixture of a carbide of intimately associated refractory metalsand an oxide of corresponding refractory metals, pressing the powderedmixture to the form of a coherent bar, furnace heating the bar to causeinteraction of the carbide and oxide at a temperature below thetemperature at which the oxide volatilizes as such, and then, after thereaction is largely completed, raising the temperature of the bar to apoint below the least high melting point of the metals constituting thealloy being produced to complete the reaction.

3. The method of producing refractory metal of the fourth and/or fifthgroups which consists in forming a carbon-oxygen balanced mixture ofcarbide and oxide of the metal being produced, and causing the carbideto be decarburized, the oxide to be reduced, and the metal to be formed,by first heating the mixture to a temperature somewhat below thetemperature at which substantial volatilization of the oxide as suchoccurs, and then, after the reaction is largely completed, heating themixture to a higher temperature below the melting point of the metalbeing produced, to complete the reaction.

4. The method of producing refractory alloys of the fourth and fifthgroups which consists in forming a carbon-oxygen balanced mixture of acarbide of intimately associated refractory metals and an oxide ofcorresponding refractory metals, and causing the carbide to bedecarburized, the oxide to be reduced, and the alloy to be formed, byheating the mixture to a temperature somewhat below the temperature atwhich substantial volatilization of the oxide as such occurs, and

then, after the reaction is largely completed,

heating the mixture to a higher temperature below the least high meltingpoint of the metals of the alloy being produced, to complete thereaction.

5. A method of producing refractory metal of the fourth and/or fifthgroups, which comprises interacting a carbide and an oxide of therefractory metal being produced, in such proportions that substantiallyall of the carbon will combine with substantially all of the oxygen toform carbon monoxide, such interaction being accomplished by firstheating the carbide and oxide to a temperature below the temperature atwhich substantial volatilization of the oxide as such occurs, and then,after the reaction is largely completed, heating to a higher temperaturewhich is below the melting point of the metal being produced, tocomplete the reaction.

6. A method of producing a refractory alloy of the fourth and/or fifthgroups which comprises interacting a carbon-oxygen balanced mixture of acarbide of intimately associated metals and an oxide of correspondingmetals to remove carbon and oxygen from the mixture, whereby to form analloy of the metals, such interaction being accomplished by firstheating the mixture to a temperature below the temperature at whichsubstantial volatilization of the oxide as such occurs, and then, afterthe reaction is largely completed, heating to a higher temperature belowthe melting points of the metals of the refractory alloy being produced,to complete the reaction.

7. The improvement in the art of producing refractory metal of thefourth and/or fifth groups, which includes pressing, to the form of acoherent bar, a carbon-oxygen balancecl powdered mixture of carbide andoxide of the metal being produced, and heating the bar to causeinteraction of the carbide and oxide at a temperature below thetemperature at which the oxide volatilizes as such.

8. The improvement in the art of producing refractory alloys of thefourth and/or fifth groups which consists in forming a carbon-oxygenbalanced mixture of a carbide of intimately associated refractory metalsand an oxide of corresponding refractory metals, pressing the powderedmixture to the form of a coherent bar, and heating the bar to causeinteraction of the carbide and oxide at a temperature below thetemperature at which the oxide volatilizes as such.

9. A method of producing a refractory metal or alloy of the fourthand/or fifth groups from compounds, ores, minerals and concentratesthereof which comprises carburizing the desired compound or the likewith sufficient carbon to form a carbide with substantially all therefractory metal content thereof, purifying the resultant ore carbide toproduce substantially all refractory metal carbide, converting a part ofthe carbide to oxide by direct ignition, mixing the oxide with thecarbide to form a substantially carbon-oxygen balanced mixture, pressingthe mixture into a bar, furnace-heating the bar to cause interaction ofthe carbide and oxide at a temperature below the temperature at whichthe oxide volatilizes as such, then after the reaction is largelycompleted raising the temperature of the bar to a higher temperaturebelow the least high melting point of the metal or metals contained inthe bar to complete the reaction, then the metal powder into a bar andsintering the bar to form a dense. coherent mass.

10. A method of producing a refractory metal or alloy of the fourthand/or fifth groups from compounds, ores, minerals and concentratesthereof which comprises carburizing the desired compound or the likewith suflicient carbon to form a carbide with substantiallyall therefractory metal content thereof, purifyingthe resultant ore carbide toproduce substantially all refractory metal carbide, converting a part ofthe carbide to oxide by direct ignition, mixing the oxide with thecarbide to form a substantially carbon-oxygen balanced mixture, pressingthe mixture into a bar and furnace-heating the bar to cause interactionof the carbide and oxide at a temperature below the temperature at whichthe oxide volatilizes as such.

11. A method of producing a refractory metal or alloy of the fourthand/or fifth groups from compounds thereof which comprises carburizingthe desired compounds with sufficient carbon to form a carbide withsubstantially all the refractory metal content thereof, purifying theresultant ore carbide to produce substantially all refractory metalcarbide, mixing the carbide with an oxide of a fourth and/or fifth grouprefractory metal to form a substantially carbon-oxygen balanced mixture,and heating the mixture to cause interaction of the carbide and oxide ata temperature below the temperature at which the oxide volatilizes assuch.

12. A method of producing a refractory metal or alloy of the fourthand/or fifth groups which comprises interacting a carbon-oxygen balancedmixture of a carbide of intimately associated metal or metals and anoxide of corresponding metal or metals to remove carbon and oxygen fromthe mixture whereby to form an alloy of the metals or a metal, suchinteraction being accomplished by first heating the mixture to atemperature below the temperature at which substantial volatilization ofthe oxides as such occurs and then, after the reaction is largelycompleted, heating to a higher temperature below the melting point ofthe metal or metals of the refractory alloy being produced to completethe reaction, thereafter hydrogenating the reaction mass to produce abrittle hydride of the metai or metals, then crushing the embrittledmass to powder, then dehydrogenating the hydride powder to form metalpowder, pressing the metal powder into a bar and sintering the bar toform a dense coherent mass. t

13. The improvement in the art of producing refractory metals or alloysof the fourth and/or fifth groups which consists in forming acarbonoxygen balanced mixture of a carbide of refractory metal orintimately associated refractory metals and an oxide of thecorresponding refractory metal or metals, pressing the mixture to theform of a coherent bar, heating the bar to a temperature below thetemperature at which substantial volatilization of the oxide as suchoccurs and then after the reaction is largely completed, heating to ahigher temperature below.

the melting point of the metal or metals of the refractory alloy beingproduced to complete the reaction and thereafter hydrogenating thereaction slug to produce brittle hydride-of the metal or alloy, thencrushing the embrittled slug to anced mixture, forming a coherent barfrom said mixture. heating the bar to cause interaction of the carbideand oxide at a temperature below the temperature at which the oxidevolatilizes as such, and then after the reaction is largely completed,heating to a higher temperature below the melting point of the metalbeing produced, to complete the reaction.

CLARENCE w. BALKE. CLAIRE 0. 3m.

